Adhesive tape, bonded composite and electrical separation method for bonded composite

Abstract

The invention relates to an adhesive tape, a bonded composite, an electrical separation method for a bonded composite, and the use of the adhesive tape for bonding components in electronic, automotive, medical and dental devices. The adhesive tape comprises at least one adhesive layer D, wherein the adhesive of the adhesive layer D is a heat-activatable adhesive and contains at least one electrolyte.

Description

[0001] The invention relates to adhesive tapes, bonded composites, methods for electrical separation of bonded composites and the use of adhesives for bonding components in electronic devices, automobiles, medical devices and dental devices.

[0002] Double-sided pressure-sensitive adhesive tapes are often used to bond metal parts to plastics. The bonding force required for this is sufficient to fix the metal parts to the plastic. Steel, stainless steel and aluminum are preferably used as metals. For example, PVC, ABS, PC or mixtures based on these plastics are used as plastics. However, the requirements for portable consumer electronics are also constantly increasing. These items are getting smaller and smaller, so that the bonding area is also reduced. These requirements are particularly problematic for metal bonding on plastics. This can be achieved in a particularly effective way by using heat-activatable films, which can form particularly high bonding strengths after activation.

[0003] For example, DE 10202100580 A1 discloses an adhesive film which is cured by heating, wherein the adhesive film is based on a formulation in an organic solvent which comprises a thermoplastic polymer which can react with isocyanates via functional groups and a corresponding isocyanate-containing crosslinker component.

[0004] Recently, there has been a growing interest in "debonding on demand" capabilities, which is due to environmental laws or end-customer awareness of sustainability and increasing cost pressure in the manufacturing industry. The application scenarios of the debonding process are divided into rework (post-processing), repair, recycling and processing assistance.

[0005] Debonding techniques aim to achieve either cohesive splitting of the adhesive layer or adhesive separation of the adhesive layer from the substrate. The former requires cleaning of the substrate prior to rebonding, while the latter does not require such cleaning.

[0006] However, adhesive separation techniques that guarantee the required high and permanently reliable adhesion are often more difficult to implement or require a long time in application, such as stripping with the aid of penetrating solvents.

[0007] At present, in particular in the rework or repair of electronic devices such as smartphones and tablets, mainly cohesive-splitting adhesive compounds (usually designed as pressure-sensitive tapes) are used, which decrease in their cohesion with increasing temperature, so that manual cohesive separation of the bond can be carried out. The result is extensive rework for preparing the substrate surface contaminated with adhesive residues for bonding again.

[0008] In addition to thermally mediated separation processes, electrical separation methods have also been discussed. For example, EP 3031875 B1 discloses reducing the adhesion (bond strength) of acrylate adhesives by applying an electrical voltage.

[0009] EP 3199344 B1 and DE 102005050632 A1 disclose the electrical reseparation of substances (compositions, Massen) applied as melt adhesives.

[0010] EP 4067401 A1 discloses a liquid two-component adhesive system which can be stripped again after bonding by electrochemical methods.

[0011] EP 4050040 A1 discloses liquid one-component adhesives which can be stripped again electrochemically by applying a voltage for 30 minutes.

[0012] US2007269659 A1 discloses a two-component adhesive which is cured by contacting the two components and then the tensile strength of the bonded uncomposite is reduced by applying a voltage of 50V.

[0013] Heat-activated adhesive connections, in particular those produced by heat-activatable adhesive tapes, generally have very high bond strengths.

[0014] Such adhesive tape solutions are therefore not removable, or not removable without damaging the substrate to which they are bonded and requiring considerable effort.

[0015] The object of the present invention is therefore to provide an adhesive tape comprising at least one adhesive layer D, wherein the adhesive of the adhesive layer D is a heat-activatable adhesive, wherein the adhesive tape should be easily removable from at least one substrate. At the same time, the adhesive strength of the adhesive tape to the substrate to be bonded should not be negatively affected before separation (detachment).

[0016] According to the invention, this object is achieved by an adhesive tape according to claim 1 .

[0017] The adhesive tape according to the invention comprises at least one adhesive layer D, wherein the adhesive of the adhesive layer D is a heat-activatable adhesive and contains at least one electrolyte.

[0018] Due to the contained electrolyte, the adhesive layer D can be electrically separated (peeled off) by applying a voltage.

[0019] Surprisingly, it has been found that heat-activatable adhesive layers comprising at least one electrolyte and thus adhesive tapes comprising heat-activatable adhesive layers can be separated again electrically without effort by applying an electrical voltage in a simple and rapid manner, and at the same time the high adhesive strength of the adhesive tape to the substrates to be bonded is not negatively affected before separation.

[0020] Adhesives and methods for electrical separation or electrical reduction of adhesion are known in principle in the prior art. Thus, as mentioned above, EP 3031875 B1 discloses such an electrical method. The electrically separable adhesive is an adhesive based on acrylates.

[0021] As mentioned above, hot melt adhesives and liquid one- and two-component systems may also be electrically separable.

[0022] However, it was unexpected that even heat-activatable adhesive tapes in the form of films with relatively high adhesion to various substrates could be electrically separated after bonding without the adhesive tape's bond strength to the substrates to be bonded being negatively affected before separation. At the same time, the separation is clean and convenient.

[0023] In particular, it was unexpected here that a relatively rigid matrix, for example a thermoplastic elastomer, in an adhesive film or tape could be designed to be electrically separable and that the electrolyte is fully compatible with the matrix and can also migrate through the matrix quickly enough without negatively affecting the bond strength.

[0024] The adhesive tape according to the invention is preferably a double-sided adhesive tape. For the sake of convenience, within the scope of the invention, the adhesive tape according to the invention is also referred to as "adhesive tape" in the double-sided embodiment.

[0025] The invention relates to adhesive tapes which can be present in any assembled form, with adhesive tape rolls being preferred. The adhesive tapes, in particular in web form, can be produced in roll form (i.e. wound on itself in the form of an Archimedean spiral) or obtained as adhesive strips (e.g. in the form of cut or die-cut pieces).

[0026] The adhesive tape according to the invention is in particular in the form of a web. A web is understood to be an object whose length (extension (extent) in the x-direction) is a multiple of its width (extension (extent) in the y-direction) and whose width is formed approximately, preferably identically, along the entire length.

[0027] The general (generic) term "adhesive tape", also synonymously referred to as "adhesive strip", in the sense of the present invention comprises all flat structures, such as foils or foil parts (foil segments) extending in two dimensions, tapes with extended length and limited width, tape parts (tape segments), etc., and finally also die-cut parts or labels.

[0028] In addition to the length (x-direction) and width (y-direction), the adhesive tape also has a thickness (z-direction) extending perpendicularly to the two extents, wherein the width and length extents are many times greater than the thickness. The thickness is as constant as possible over the entire area determined by the length and width of the adhesive tape, preferably completely identical within a tolerance range.

[0029] These embodiments apply analogously to the carrier layer which, according to a preferred embodiment, forms a layer in the x and y direction as a component of the adhesive tape.

[0030] It will be appreciated that the layers are arranged on top of each other in the z-direction.

[0031] All embodiments of the present description apply to the adhesive tape according to the invention, to the method according to the invention for producing an adhesive tape, to the adhesively bonded composite according to the invention, to the method according to the invention for producing an adhesively bonded composite and to the method for electrical separation of a composite and to the use of the adhesive tape according to the invention.

[0032] The invention also includes all features that are the subject of any dependent claims. Furthermore, the invention includes combinations of individual features with one another and, in this case, also different levels of preference. Thus, for example, the invention includes a combination of a first feature that is referred to as "preferred" with a second feature that is referred to as "particularly preferred". Here, the subject matter that is also referred to as being within the framework (scope) of an "embodiment" also includes different levels of preference.

[0033] Next, the adhesive of the adhesive layer D will be described in more detail.

[0034] The adhesive layer D contains at least one electrolyte.

[0035] "Electrolyte" is understood here to mean a compound "which dissociates into ions in the solid, liquid or dissolved state and moves in a directed manner under the influence of an electric field", as listed under the Wikipedia entry "Electrolyte" on January 4, 2023.

[0036] Preferably, the electrolyte of the adhesive layer D is selected from ionic liquids and metal salts, with ionic liquids being particularly preferred.

[0037] In particular, one or more ionic liquids as electrolytes make it possible to easily re-detach the adhesive tape without negatively affecting the adhesive properties of the adhesive tape. Ionic liquids have the advantage that they are well and evenly distributed in the polymer matrix of the adhesive and re-detach more quickly than with other electrolytes.

[0038] In addition, the components of ionic liquids are non-volatile, particularly at room temperature. Ionic liquids are also relatively thermally stable and are non-flammable and relatively chemically stable.

[0039] In the context of the present invention, ionic liquids are salts which are liquid at room temperature, ie at 23° C. Ionic liquids accordingly comprise anions and cations.

[0040] Ionic liquids are therefore particularly suitable as electrolytes within the context of the separation method or electrical separation method according to the invention.

[0041] When a voltage is applied, anions move to the anode side and cations move to the cathode side. Without intending to be limited thereto, it can be mechanically assumed that this results in a reduction in the adhesion of the adhesive layer containing the ionic liquid to at least one substrate, thereby achieving adhesive cleavage between the adhesive and at least one substrate.

[0042] In principle, all ionic liquids are suitable within the scope of the present invention.

[0043] The ionic liquid used within the scope of the present invention comprises at least one anion and at least one cation. Here, it is also conceivable that the ionic liquid comprises two or more types of anions and / or two or more types of cations. In addition, it is conceivable that two or more different ionic liquids are added to the adhesive layer D or that the adhesive layer D then comprises two or more different ionic liquids.

[0044] Preferably, the anion of the ionic liquid is selected from: Br - 、AlCl4 - 、Al2Cl7 - 、NO3 - 、BF4 - PF6 - 、CH3COO - CF3COO - CF3CO3 - CF3SO3 - 、(CF3SO2)2N - 、(CF3SO2)3C - 、AsF6 - 、SbF6 - CF3(CF2)3SO3 - (CF3CF2SO2)2N - 、CF3CF2CF2COO - 、(FSO2)2N - .

[0045] Surprisingly, in particular in reactive heat-activatable adhesives, a particularly high reduction in the bond strength and thus particularly good electrical separability of the adhesive tape according to the invention is achieved by applying a voltage. In particular, (re)separation is achieved particularly quickly and without residues with these anions.

[0046] Particularly preferably, the anion is selected from: (CF3SO2)2N - and (FSO2)2N - .

[0047] These anions are particularly suitable because they achieve an optimal electrical separability. In particular, with these anions the (re)separation is achieved particularly quickly and without residues.

[0048] Preferably, the cation of the ionic liquid is selected from the group consisting of imidazolium-based cations, pyridinium-based cations, pyrrolidine-based cations and ammonium-based cations.

[0049] Surprisingly, in particular in reactive heat-activatable adhesives, a particularly high reduction in the bond strength and thus particularly good electrical separability of the adhesive tape according to the invention is achieved by applying a voltage. In particular, (re)separation is achieved particularly quickly and without residues with these anions.

[0050] Particularly preferably, the cation is selected from imidazolium-based cations.

[0051] These cations are particularly suitable because they achieve an optimal electrical separability. In particular, with these anions, (re)separation is achieved particularly quickly and without residues.

[0052] Very particularly preferably, the cation is selected from 1-ethyl-3-methylimidazolium and 1-butyl-3-methylimidazolium, and again preferably, the cation is 1-ethyl-3-methylimidazolium.

[0053] Particularly preferably, the electrolyte of the adhesive layer D is selected from the following ionic liquids: 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-TFSI) and 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMIM-FSI).

[0054] Surprisingly, in particular in reactive heat-activatable adhesives, a particularly high reduction in the bond strength and thus particularly good electrical separability of the adhesive tape according to the invention is achieved by applying a voltage. In particular, (re)separation is achieved particularly quickly and without residues with these anions.

[0055] Preferably, the first adhesive layer D contains 1 to 10% by weight, particularly preferably 2 to 8% by weight, of an electrolyte, preferably an ionic liquid, based on the total amount of the adhesive.

[0056] The use of electrolytes, in particular ionic liquids, in preferred or particularly preferred amounts of this type enables relatively fast electrical separation, while at the same time the adhesion of the adhesive layer to the adjacent layer, in particular at least one substrate, is not negatively affected before separation.

[0057] The material of the adhesive layer D is a heat-activatable adhesive.

[0058] Heat-activatable adhesives can be divided in principle into two categories, namely purely physical heat-activatable adhesives and reactive heat-activatable adhesives.

[0059] Physical heat-activatable adhesives

[0060] This type of adhesive, also known as "hot melt adhesive", has no or weak self-adhesive properties at room temperature. The adhesive is only activated when heated and in this case has self-adhesive properties. The reason for this is the correspondingly high glass transition temperature of the adhesive, so that the activation temperature for achieving sufficient adhesiveness (usually several tens to several hundred degrees Celsius) is above room temperature. Due to its self-adhesive properties, the adhesive effect is produced even before the solidification of the substance. After the adhesive partners have been joined together, physically heat-activatable adhesives physically bond during the cooling process under consolidation (solidification), so that the adhesive effect is maintained in the cold state and the actual adhesive force is formed there.

[0061] The more heat, pressure and / or time are applied during bonding, the stronger the bond between the two materials to be bonded will generally be. In this way, the maximum bond strength can generally be achieved under technically light processing conditions.

[0062] Physical melting achieves a high bond strength and thus a bonding effect. These substances are therefore purely physical heat-activatable adhesives.

[0063] Reactive heat-activated adhesives

[0064] Reactive heat-activatable adhesives (also called "reactive adhesives") are polymer systems with functional groups that chemically react when heated, wherein the adhesive chemically bonds and develops greater internal strength.

[0065] It may also be advantageous to design reactive adhesives in such a way that they become softer and / or more flowable at elevated temperatures in order to optimally adapt to the adhesive bond; this is particularly preferably achieved with thermoplastic components.

[0066] Through the above-mentioned chemical reaction and physical melting, a high bonding strength is achieved, and thus an adhesive effect is achieved.

[0067] Preference is therefore given to adhesive tapes according to the invention in which the heat-activatable adhesive of the adhesive layer D is a reactive heat-activatable adhesive or a physical heat-activatable adhesive.

[0068] As can be inferred from the term "heat-activatable", the activation leading to the adhesive effect is achieved by heating. This means that these adhesives are not activated at room temperature, in particular at 23° C., that is, the effect leading to a permanent bond is not triggered (initiated).

[0069] Preference is given to adhesive tapes according to the invention in which the heat-activatable adhesive is activated only at temperatures of 50° C. or higher, and preferably at temperatures of 50° C. to 200° C. Therefore, “heat-activatable” is preferably understood to mean that activation takes place at temperatures of 50° C. or higher, and preferably at temperatures of 50° C. to 200° C.

[0070] According to an advantageous embodiment of the invention, the heat-activatable adhesive is activated only at temperatures of 50° C. or higher, preferably 60 to 130° C., particularly preferably 70 to 120° C., very particularly preferably 75 to 110° C.

[0071] According to a further advantageous embodiment of the invention, the heat-activatable adhesive is activated only at temperatures of 130° C., preferably 150° C. or higher.

[0072] The duration of the activation is preferably from 10 seconds to 10 minutes, particularly preferably from 10 seconds to 8 minutes.

[0073] According to a preferred embodiment of the present invention, the duration is 40 seconds to 8 minutes.

[0074] According to a preferred embodiment of the present invention, the duration is 30 seconds to 6 minutes, particularly preferably 60 seconds to 3 minutes.

[0075] Through these relatively short activation times, a rapid and very stable bond is achieved.

[0076] In this case, preferably at high activation temperatures in the above-mentioned temperature range a correspondingly shorter activation duration is selected, and at low temperatures a correspondingly longer activation duration is selected. This also depends in particular on the bond strength to be achieved.

[0077] Furthermore, the activation is preferably carried out using pressure, also referred to as compression pressure. The compression pressure is preferably 1 to 15 bar, particularly preferably 2 to 12 bar.

[0078] According to a preferred embodiment of the present invention, the compression pressure is 2 to 5 bar.

[0079] According to a further preferred embodiment of the present invention, the compression pressure is 4 to 6 bar, in particular 5 bar, for example.

[0080] According to a further preferred embodiment of the present invention, the compression pressure is 5 to 10 bar, in particular 6 bar or 10 bar, for example.

[0081] Prior to activation, so-called pre-lamination is preferably carried out in order to achieve optimal wetting of the substrates. This is achieved in particular by preheating the substrates to be bonded.

[0082] In this case, preferably in the case of physically heat-activatable adhesives, the substrates to be bonded are heated to a temperature of 60 to 90° C. The adhesive layer is preferably applied to the respective substrate with a pressure of 1 to 5 bar for more than 5 seconds.

[0083] This ensures that the adhesive flows evenly onto the substrate before activation.

[0084] Preferably, in the case of reactive, heat-activatable adhesives, the substrates to be bonded are heated to a temperature of 50° C. to 70° C. The adhesive layer is preferably applied to the respective substrate with a pressure of 1 to 3 bar for 5 to 20 seconds.

[0085] This ensures that the adhesive flows evenly onto the substrate before activation.

[0086] Preference is given to adhesive tapes according to the invention in which the heat-activatable adhesive of the adhesive layer D comprises a polymer component consisting of at least one thermoplastic elastomer. Thermoplastic elastomers can in principle be all thermoplastic polymers suitable for heat-activatable adhesives, such as in particular polyurethanes, polyesters, polyamides.

[0087] Particularly preferably, the thermoplastic elastomer is thermoplastic polyurethane (TPU).

[0088] According to a preferred embodiment of the invention, the polyurethane is a semicrystalline polyurethane, wherein the adhesive is preferably a physically heat-activatable or reactively heat-activatable adhesive.

[0089] Suitable polyurethanes are, for example, HYDROGEN® from Covestro AG. U family or The commercially available products of the family, such as U53 or 530.

[0090] Particularly preferably, the heat-activatable adhesive of the adhesive layer D is a reactive heat-activatable adhesive.

[0091] Reactive heat-activatable adhesives can be based on different polymers as well as crosslinking chemicals and crosslinking mechanisms.

[0092] According to an advantageous embodiment of the invention, the polymer component is formed here from at least one polymer containing functional groups reactive with isocyanates. The reactive heat-activatable adhesive of the adhesive layer D also comprises a crosslinker component formed from at least one isocyanate-containing compound.

[0093] The polymer here is in particular a thermoplastic elastomer, preferably a thermoplastic polyurethane and in turn preferably a semicrystalline thermoplastic polyurethane.

[0094] Functional groups reactive toward isocyanates are, for example, in particular hydroxyl, amino or urethane groups.

[0095] According to a particularly preferred embodiment of the present invention, the functional group is a hydroxyl group.

[0096] Surprisingly, reactive, heat-activatable adhesives of this type can be electrically separated again particularly well after bonding, wherein the bond strength is greatly reduced by applying an electrical voltage.

[0097] Furthermore, the separation takes place in a clean manner; this means that no residues of adhesive remain on the substrate or can be removed in a simple manner, for example manually.

[0098] Furthermore, it was surprisingly found that, depending on the type and area of ​​the adhesive residue, it can also be reused without removal and the substrate can thereby be re-bonded via the residue, which in turn brings ecological benefits.

[0099] According to a preferred embodiment of the present invention, toluene diisocyanate compounds (TDI compounds) are used as isocyanate-containing components, for example TDI dimer (for example as Dispercoll BL XP (aqueous dispersion of reactive isocyanates based on TDI dimer; in the present case preferably used after removal of the water) or as Dancure (1,3-bis(3-isocyanato-4-methylphenyl)-1,3-diazetidine-2,4-dione; solid)), and / or isophorone diisocyanate (IPDI).

[0100] The heat-activatable adhesive preferably contains 1% to 25% by weight, particularly preferably 2% to 15% by weight, particularly advantageously 4% to 10% by weight, of isocyanate-containing compounds, based on the total amount of the adhesive.

[0101] The reactive, heat-activatable adhesives here can be obtained from aqueous (water-containing) compositions or compositions based on organic solvents.

[0102] According to a preferred embodiment of the invention, the reactive heat-activatable adhesive is a water-based adhesive.

[0103] According to a further preferred embodiment of the invention, the reactive heat-activatable adhesive is a solvent-based adhesive.

[0104] According to an advantageous embodiment of the invention, the reactive heat-activatable adhesive of the adhesive layer D preferably further comprises at least one additional component from the group of epoxides and / or epoxy compounds.

[0105] Preference is given to mono-, di-, tri- or polyfunctional epoxides and / or epoxy compounds. These include, for example, liquid / viscous compounds at 23° C. such as N,N,N′,N′-tetrakis(2,3-epoxypropyl)-m-xylene-a,a′-diamine and / or 7-oxabicyclo-[4.1.0]hept-3-ylmethyl 7-oxabicyclo[4.1.0]heptane-3-carboxylate and / or compounds having a melting / softening point above 23° C. (so-called epoxy / epoxy resins) such as Epiclon N-673.

[0106] For example, bisphenol F epoxy resins are particularly suitable, which are marketed under the trade name The series obtained.

[0107] According to a further advantageous embodiment of the invention, the heat-activatable adhesive of the adhesive layer D is a reactive heat-activatable adhesive and further comprises at least one peroxide. Here too, preferably thermoplastic polyurethane is contained as polymer component.

[0108] The peroxide preferably has the general formula ROO-R', wherein R and R' represent an organic group individually or together represent a cyclic organic group.

[0109] According to the general understanding of those skilled in the art, an organic group is an organic chemical residue (group) having at least one free valence at a carbon atom.

[0110] The peroxide is particularly preferably dicumyl peroxide. The adhesive tape is thereby made particularly storage-stable and resistant to moisture and heat.

[0111] It is also possible to use two or more peroxides. In a preferred procedure, dicumyl peroxide is then selected as one of the two or more peroxides.

[0112] The adhesive of the adhesive layer D may also contain further customary additives such as adhesion promoters, for example in particular silane adhesion promoters, compatibilizers, emulsifiers, thickeners, fillers, pigments, amines and age inhibitors.

[0113] According to an advantageous embodiment of the invention, the adhesive layer D comprises at least one silane adhesion promoter, preferably in particular in combination with at least one peroxide as crosslinking chemical.

[0114] Preferably, alkoxysilanes, in particular trialkoxysilanes, dialkoxysilanes and / or monoalkoxysilanes, particularly preferably trialkoxysilanes, are used as silane adhesion promoters. Examples of suitable trialkoxysilanes are trimethoxysilane and triethoxysilane.

[0115] Preferably, for example, triethoxysilane, 3-methacryloxypropyltriethoxysilane are used as silane adhesion promoters.

[0116] The amount of the at least one silane adhesion promoter is preferably 0.5 to 20% by weight, particularly preferably 1 to 10% by weight, very particularly preferably 1.5 to 5% by weight, in particular 2.5 to 3.5% by weight, based on the total amount of the adhesive.

[0117] Thickeners are used in particular as additives in aqueous or water-based systems. Before the water evaporates, ie before the adhesive tape is dried, the thickeners act as rheology modifiers.

[0118] Low molecular weight polyethers such as polyethylene glycol (PEG) and / or polypropylene glycol (PPG), polyamines, polyvinyl pyrrolidone or aliphatic polyesters are preferably used as compatibilizers, which are homogeneously miscible with the adhesive.

[0119] Another subject of the invention is a bonded composite comprising at least the following layers:

[0120] A first substrate A; and

[0121] A second substrate B; and

[0122] The adhesive tape according to the present invention, which is arranged between a substrate A and a substrate B and bonds the substrates A and B to each other.

[0123] Another subject of the present invention is a method for the electrical separation of the complexes according to the invention, comprising at least the following method steps:

[0124] i.) applying a voltage at two different sites of the complex, wherein the voltage is preferably 2 to 50V.

[0125] The application of voltage is carried out according to step i.) of the method for electrical separation of complexes according to the invention.

[0126] In particular, the voltage is a DC voltage.

[0127] According to a preferred embodiment of the invention, the voltage is 3 to 12 V. Such a voltage can in particular be applied by using a battery located in the vicinity of the bond, such as in particular and for example in mobile phones, tablet computers and the like.

[0128] According to a further preferred embodiment of the invention, the voltage is 12 to 50 V. This relatively high voltage allows particularly rapid separation; the voltage may only be applied for a few seconds.

[0129] A skilled person generally knows how to apply voltage without causing an undesired short circuit.

[0130] Depending in particular on the selected voltage, the duration of application of the voltage in step i.) can be a few seconds, in particular 2 seconds, up to 900 seconds, preferably up to 600 seconds, particularly preferably up to 300 seconds.

[0131] Of course, it is also conceivable that the voltage may be applied for a period of time exceeding 900 seconds, particularly when the voltage is relatively low.

[0132] The method according to the invention for electrically separating the composite according to the invention makes it possible to separate the substrates A and B from one another quickly and easily without requiring great expenditure of effort.

[0133] If, after application of the voltage, the layers do not separate from one another without further action, the method according to the invention comprises at least the further method steps:

[0134] ii.) applying force to the adhesive layer D and / or the substrate A and / or the substrate B, thereby increasing the distance between the substrates A and B.

[0135] The force which may still be required according to step ii.) is significantly lower than the adhesive force before the application of the voltage according to step i.).

[0136] The application of the voltage according to step i.) is carried out at two different points of the bonded composite according to the invention. The point at which the voltage is applied appropriately depends on the construction of the adhesive tape and the bonded composite and therefore on the properties of the individual layers and the mutually bonded substrates A and B.

[0137] Hereinafter, some preferred embodiments are implemented.

[0138] According to a preferred embodiment, the adhesive tape is a transfer tape and consists of an adhesive layer D.

[0139] This adhesive tape can be advantageously electrically separated again in a bonded composite with two substrates A and B in the following manner: both substrate A and substrate B are conductive. For this purpose, a voltage is applied to substrates A and B so that migration of anions to the anode and cations to the cathode occurs in the adhesive. Without wishing to be bound by a particular theory, the inventors assume the following mechanism: by applying a voltage, migration of electrolytes, in particular separation of anions and cations of ionic liquids, occurs in the adhesive layer D. Thus, the adhesion of the adhesive layer D to substrates A and B is greatly reduced and these layers are separated (loosened) from each other.

[0140] According to a preferred embodiment of the invention, the bonded composite thus comprises the following layers:

[0141] a first substrate A which is electrically conductive; and

[0142] a second substrate B which is electrically conductive; and

[0143] The adhesive tape according to the present invention, which is composed of an adhesive layer D and is arranged between a substrate A and a substrate B, and bonds the substrates A and B together.

[0144] According to a further preferred embodiment, in addition to the first adhesive layer D, the adhesive tape comprises at least one second adhesive layer C.

[0145] According to a particularly preferred embodiment of the invention, the second adhesive layer C is conductive. This structure has the advantage that a voltage can be applied to the adhesive layer C, so that the non-conductive substrate, here the substrate B, can also be electrically separated again.

[0146] According to a preferred embodiment of the invention, the adhesive layer C here projects laterally beyond the substrate to which it is bonded, so that a voltage can be applied to the layer C from above, ie close to the substrate.

[0147] According to a preferred embodiment of the invention, the substrate to which the layer C is bonded, here substrate B, has holes, so that here the adhesive layer C also protrudes laterally from the substrate to which it is bonded. Here, the voltage can also be applied to the layer C from above, ie close to the substrate.

[0148] This possibility is particularly advantageous when the layer C is designed to be so thin that lateral application to this layer is not possible. Otherwise, correspondingly thin electrodes can also be used.

[0149] According to a particularly preferred embodiment of the invention, the second adhesive layer C is also a reactive heat-activatable adhesive. As a result, the adhesive tape can continue to be used for those substrates or applications that require reactive heat-activatable adhesive tapes. In addition, the first adhesive layer D and the second adhesive layer C are therefore particularly compatible.

[0150] Preferably, according to the above-described embodiment, the adhesive tape consists of layers D and C. The structure comprising the second adhesive layer is also referred to below as a two-layer composite DC.

[0151] According to a preferred embodiment, layer D in the xy plane has the same dimensions as layer C, so that D and C can be processed together as a two-layer composite and, for example, stamped.

[0152] According to a preferred embodiment of the invention, the bonded composite thus comprises the following layers:

[0153] a first substrate A which is electrically conductive; and

[0154] A second substrate B; and

[0155] An adhesive tape according to the invention which consists of a two-layer composite DC and in which the substrates A and B are bonded to one another in such a way that the adhesive layer D is bonded to the electrically conductive substrate A.

[0156] As mentioned above, the substrate B does not have to be electrically conductive in this case. According to a preferred embodiment, the substrate B is electrically non-conductive in this case.

[0157] According to a further preferred embodiment, in addition to the first adhesive layer D, the adhesive tape further comprises at least the following layers:

[0158] A second adhesive layer C; and

[0159] • At least one electrically conductive carrier layer T arranged between layers D and C.

[0160] Such an adhesive tape can be used as a double-sided adhesive tape for a wide variety of substrates via the second adhesive layer C. In principle, this can be the same substrate as in the previous embodiment in which the adhesive tape is a transfer tape.

[0161] Furthermore, such an adhesive tape can be used in particular and also advantageously for later separation of substrates A and B from one another, wherein only one substrate, for example substrate A, is electrically conductive.

[0162] According to a preferred embodiment, either xi.) only the carrier layer T or xii.) the carrier layer T and the second adhesive layer C are designed to be electrically conductive.

[0163] Thus, a voltage can be applied to xi.) the electrically conductive carrier layer or to xii.) the second adhesive layer C and the electrically conductive substrate A.

[0164] The tape is advantageously previously bonded as a double-sided tape, so that the electrically separable adhesive layer D is bonded to the conductive substrate A and the second adhesive layer is bonded to the substrate B, which can be conductive, but need not be.

[0165] Without wishing to be bound by a particular theory, the inventors assume the following mechanism: by applying a voltage, migration of electrolytes, in particular separation of anions and cations of the ionic liquid, occurs in the adhesive layer D. As a result, the adhesion of the adhesive layer D to the substrate A is greatly reduced and the layers are separated (loosened) from each other.

[0166] According to a preferred embodiment of the invention, xi.) only the carrier layer is electrically conductive. In particular and preferably, a voltage can be applied to the carrier layer particularly effectively when the carrier layer protrudes laterally beyond the at least one adhesive layer.

[0167] According to a further preferred embodiment of the invention, xii.) the carrier layer and the second adhesive layer C are electrically conductive. This structure has the advantage that a voltage can be applied to the adhesive layer C. Lateral projections of the carrier layer are unnecessary. The adhesive tape can thus be produced in a simple manner, in particular because the layers D, T and C can be stamped (die-cut) together.

[0168] Preferably, according to the above-described embodiment, the adhesive tape consists of three layers D, T and C. For this reason, the term three-layer composite DTC is also used within the scope of the present application.

[0169] According to a preferred embodiment of the invention, the bonded composite thus comprises the following layers:

[0170] a first substrate A which is electrically conductive; and

[0171] A second substrate B; and

[0172] An adhesive tape according to the invention, which consists of a three-layer composite DTC, and the substrates A and B are bonded to one another in such a way that the adhesive layer D is bonded to the electrically conductive substrate A.

[0173] According to a further preferred embodiment, the adhesive tape comprises at least the following layers in addition to the first adhesive layer D:

[0174] A second adhesive layer C; and

[0175] at least one first electrically conductive carrier layer T arranged between layers D and C; and

[0176] at least one second electrically conductive carrier layer T′ arranged on the face of said adhesive layer D opposite to the first electrically conductive carrier layer T; and

[0177] • A third adhesive layer C' arranged on the face of the second electrically conductive carrier layer T' opposite to the first adhesive layer D.

[0178] This adhesive tape has at least a layer structure CTD-T'-C' and can be used as a double-sided adhesive tape for various substrates via the adhesive layers C and C'.

[0179] In principle, this can be the same substrate as in the previous embodiment, wherein the adhesive tape is a transfer tape or has a three-layer structure DTC.

[0180] However, such an adhesive tape can also be used in particular and advantageously to later separate substrates A and B from one another, wherein neither substrate A nor B is electrically conductive.

[0181] According to a preferred embodiment, either xi.) only the carrier layers T and T′ or xii.) the carrier layers T and T′ and the second adhesive layer C and / or the third adhesive layer C′ are designed to be electrically conductive.

[0182] A voltage can thus be applied to xi.) both electrically conductive carrier layers or xii.) to at least one adhesive layer C and C′ and to one of the carrier layers or to the other adhesive layer.

[0183] Similar to the above embodiment, it is assumed that by applying a voltage, migration of electrolytes, in particular separation of anions and cations of the ionic liquid, occurs in the adhesive layer D. As a result, the adhesion of the adhesive layer D to the conductive support layers T and T' is greatly reduced and these layers are separated (loosened) from each other.

[0184] According to a preferred embodiment of the invention, xi.) only the carrier layers T and T' are electrically conductive. In particular and preferably, a voltage can be applied to the carrier layers T and T' particularly effectively when the carrier layers T and T' protrude laterally beyond at least one of the respective adjacent adhesive layers.

[0185] According to a further preferred embodiment of the invention, xii.) the carrier layers T and T' and the second and third adhesive layers C or C' are electrically conductive. This structure has the advantage that a voltage can be applied to the adhesive layers C and C'. Lateral projections of the carrier layers T and T' are unnecessary. Thus, the adhesive tape can be manufactured in a simple manner, in particular because the layers C, T, D, T' and C' can be stamped (die-cut) together.

[0186] Preferably, according to the above-described embodiment, the adhesive tape consists of five layers C, T, D, T' and C'. For this reason, within the scope of the present application, the term five-layer composite CTD-T'-C' is also used.

[0187] According to a preferred embodiment of the invention, the bonded composite thus comprises the following layers:

[0188] A first substrate A; and

[0189] A second substrate B; and

[0190] An adhesive tape according to the invention, which consists of five layers of the composite CTD-T'-C' and in which the substrates A and B are bonded to one another.

[0191] The conductive substrate of all embodiments may be, for example, a metal housing of a mobile phone.

[0192] The non-conductive substrate of all embodiments can be, in particular, a housing made of non-conductive material, such as plastic, or a battery or other components of non-conductive design, such as a loudspeaker.

[0193] A further subject matter of the present invention is the use of the adhesive tape according to the invention for bonding components in electronic devices, vehicles, medical devices and dental devices.

[0194] The carrier layers T as well as T and T' of all the above-described embodiments are electrically conductive.

[0195] In the following, these layers are further explained. For simplicity, the term "conductive carrier layer" or even just "carrier layer" is used. According to the above embodiments, this refers to the carrier layer T or the carrier layers T and T'.

[0196] The carrier layers T and T′ are independent of one another and can be designed identically or differently from one another.

[0197] Preferably, the electrically conductive carrier layer comprises at least one metal.

[0198] Particularly preferably, the metal is selected from the group consisting of copper, nickel, zinc, tin, silver, gold, aluminum, iron, chromium and alloys of these metals. Very particularly preferably, the metal is selected from the group consisting of aluminum, copper and nickel. Aluminum is very preferred.

[0199] Preferably, the electrically conductive carrier layer has a layer thickness measured in the z direction, ie parallel to the stacking direction of the layer arrangement, of 10 nm (nanometers) to 50 μm (micrometers).

[0200] According to a preferred embodiment of the present invention, the conductive carrier layer comprises a) at least one metal foil, preferably an aluminum foil, and / or b) at least one conductive textile, which comprises at least one metal, preferably a metal selected from copper and nickel, and / or c) one or more layers of at least one vapor-deposited metal, which is preferably selected from copper and aluminum, and / or d) at least one metal grid and / or e) a foil vapor-deposited with a metal.

[0201] In principle, it is also conceivable here for the layer T to have a combination of two or more of the abovementioned possibilities.

[0202] Metal foils, such as and preferably aluminum foils, are known to those skilled in the art.

[0203] Preferably, the metal foil, for example and preferably an aluminum foil, has a layer thickness measured in the z direction, ie parallel to the stacking direction of the layer arrangement, of 5 to 50 μm, particularly preferably of 10 to 30 μm.

[0204] Conductive textiles are known to the person skilled in the art, in particular by the English expression “conductive mesh”. Here, for example, they are textile fabrics made of PET (polyethylene terephthalate) which are coated with metal, for example copper and / or nickel, thereby producing the electrical conductivity of the fabric.

[0205] It is also known to those skilled in the art that the metal can be vapor-deposited as a single layer or multiple layers directly onto a surface, such as the surface of the adhesive layer in this case.

[0206] Within the scope of the present invention, the electrically conductive support layer can be provided by evaporation of the metal onto the adhesive layer D or the adhesive layer C or the adhesive layer C′.

[0207] Furthermore, metal grids of different sizes are known to the person skilled in the art.Metal grids with appropriate layer thicknesses can be produced, for example, by a mesh composed of corresponding thin metal wires or by punching out at least one foil of corresponding layer thickness.

[0208] In the case of metal-deposited foils, in particular, non-conductive foils are metal-deposited to make them conductive. The material of the foil can in principle be selected from all materials that are suitable for metal deposition and used as carrier foil in the adhesive tape. The material is selected in particular from polyesters and polyolefins, wherein mixtures of various materials are conceivable. As polyesters, in particular polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) are preferred. As polyolefins, in particular polypropylene (PP), polyethylene (PE) are preferred. According to a preferred embodiment, the material of the foil is selected from PET, PEN, PE, PP.

[0209] Preferably, it is a foil made of PET (polyethylene terephthalate). Such a foil is dimensionally stable and can therefore be easily processed without significant stretching or tearing. This makes it possible to apply a uniform and gap-free metal layer permanently (permanently), so that electrical conductivity, in particular in the z-direction, is permanently (permanently) ensured over the entire foil.

[0210] In embodiments in which at least one electrically conductive carrier layer T or at least two electrically conductive carrier layers T and T' is present, it is preferred that these protrude laterally beyond at least one adjacent adhesive layer in at least one extension direction of the layer plane and thus have a lateral protrusion. A voltage can then be applied in a simple manner to this lateral protrusion.

[0211] In the case of a five-layer composite, according to an advantageous embodiment, the lateral projections of the electrically conductive carrier layers T and T' are spatially separated from one another. This makes it easier to apply a voltage to these two projections.

[0212] In the case of a deposited metal as a carrier layer, it is preferred that the carrier layer only protrudes laterally from the adjacent adhesive layer in at least one extension direction of the layer plane and the other adhesive layer is used accordingly as a mechanical support for the metal layer. Here, the metal layer has no actual carrier function (support function). On the contrary, the other adhesive layer serves as a carrier for the metal layer. However, for simplicity, the term carrier layer is still retained for the metal layer in these embodiments. Preferably, in this case, the layer thickness of layer T is greater than or equal to 10 nm (nanometer), preferably 50 to 200 nm.

[0213] According to a preferred embodiment of the present invention, the conductive carrier layer T or T and / or T' has a) at least one metal foil, preferably an aluminum foil, and / or b) at least one conductive textile, which has at least one metal, preferably a metal selected from copper and nickel, and / or d) at least one metal grid and / or e) a foil evaporated with metal, and protrudes in at least one extension direction beyond the first adhesive layer D and the second adhesive layer C or the first adhesive layer D and the second adhesive layer C and / or the first adhesive layer D and the third adhesive layer C'.

[0214] As a result, a voltage can be applied to the carrier layer in a simple and safe manner. At the same time, the adhesive tape can be produced in a relatively simple manner.

[0215] According to a preferred embodiment of the invention, the electrically conductive carrier layer T or T and / or T′ comprises one or more layers, preferably one layer, of at least one vapor-deposited metal, preferably a metal selected from the group consisting of copper and aluminum.

[0216] According to a particularly preferred embodiment of the present invention, the electrically conductive carrier layer T or T and / or T' comprises e) a foil on which metal is evaporated and protrudes in at least one extension direction beyond the first adhesive layer D. In this case, the foil is in particular evaporated with metal on the surface, and the respective carrier layer is bonded to the first adhesive layer D and thus to the electrically separable layer via the metallized surface.

[0217] As a result, a voltage can be applied to the carrier layer in a simple and safe manner.

[0218] The expression "protruding laterally" refers within the scope of the present invention to any type of lateral protrusion of the layer or layers described and means that the layer described extends in particular in the "xy" plane and therefore extends laterally - perpendicularly to the stacking direction - further than a reference layer. In the scope of the present invention, the terms "lateral extension" or "lateral extension" are also used instead of the term "lateral protrusion".

[0219] The term "laterally" here refers to any extension direction of the layer plane "xy" perpendicular to the stacking direction of the layer "z". The term is therefore in particular independent of the geometric shape of the adhesive tape in the "xy" plane, which can be, for example, rectangular, as is customary for adhesive tapes (see above), but also square or circular.

[0220] Slight changes in the dimensions of the individual layers in the “xy” plane due to punching methods or similar forming methods are not mentioned here, particularly since such slight material protrusions are not suitable for the intended application of voltage due to their size.

[0221] The adhesive layer C or C and C' can in principle be based on the same substances as the adhesive layer D, wherein the adhesive of the layer C or C and C' does not necessarily have to contain an electrolyte, but can do so. Preferably, the layer C or C and C' contains no electrolyte.

[0222] According to some of the above-described embodiments of the two-layer composite DC, the adhesive layer C is electrically conductive.

[0223] According to some of the above-described embodiments of the three-layer composite DTC, the adhesive layer C is electrically conductive.

[0224] Similarly, the adhesive layer C and / or the adhesive layer C' of the five-layer composite CTD-T'-C' may be designed to be electrically conductive.

[0225] In the following, these layers are further explained. For the sake of simplicity, the term "conductive adhesive layer" is used where appropriate. According to the above-mentioned embodiment, this relates to the adhesive layer C or the adhesive layer C and / or C'. In addition, for the sake of simplicity, the expression "adhesive layer C or C and / or C'" is used to refer to the corresponding layer in the embodiment of the adhesive tape comprising at least a two-layer composite, a three-layer composite or at least a five-layer composite.

[0226] The adhesive layers C and C' are independent of each other and may be the same as or different from each other.

[0227] Preferably, the electrically conductive adhesive layer contains at least one metal, such as in particular nickel, copper, silver, preferably in the form of electrically conductive metal particles and / or metallized particles, particularly preferably metal particles.

[0228] The metallized particles are in particular and preferably glass or polymer particles which are metallized with at least one metal, so that the previously non-conductive particles are made conductive by the metallization.

[0229] Particularly preferably, the conductive adhesive layer contains conductive particles selected from nickel particles, copper particles and silver-plated copper particles.

[0230] According to a particularly preferred embodiment, the conductive adhesive layer contains nickel particles.

[0231] The conductive adhesive layer preferably contains 5 to 65% by weight, particularly preferably 20 to 62% by weight, of conductive particles, in particular metal particles and / or metallized particles, based on the total amount of adhesive.

[0232] The conductive particles should preferably be no larger or no significantly larger than the corresponding thickness of the conductive adhesive layer in the z direction measured with an optical microscope.

[0233] Preferably, the electrically conductive particles have an average particle size of 1 to 10 μm, particularly preferably 1 to 6 μm, further preferably 3 to 5 μm, such as in particular 4 μm.

[0234] The conductive adhesive layer is in particular electrically conductive at least in the z-direction.

[0235] However, it can also be conductive in the xy plane. When the conductive adhesive layer is designed to be conductive only in the z direction, but not necessarily in the xy direction, according to a preferred embodiment in which metals, in particular metal particles, are added to achieve conductivity, small amounts of these materials are required. As a result, the adhesive is optimized with respect to the required conductivity, adhesion, flow behavior and cost.

[0236] According to standard MIL-DTL-83528C, a layer is then considered to be “conductive” within the scope of the invention in particular if the resistance measured in the corresponding direction (here in particular the z direction) is less than 1 ohm.

[0237] The following embodiments apply regardless of whether the adhesive layer C or C and / or C′ is designed to be electrically conductive.

[0238] According to a preferred embodiment of the invention, the adhesive layer C or C and / or C′, like the adhesive layer D, is a reactive heat-activatable adhesive, in particular based on at least one thermoplastic polyurethane which reacts with a crosslinker component upon heating.

[0239] According to a preferred embodiment of the present invention, the same polymer and crosslinking agent components as those in the adhesive layer D are used in the adhesive layer C or C and / or C′.

[0240] In this way, in particular similar substrates, referred to here as A and B, can be bonded to one another.

[0241] According to a further preferred embodiment of the present invention, an adhesive different from the adhesive of the adhesive layer D is used in the adhesive layer C or C and / or C′.

[0242] The properties of the conductive layer can thus be adapted particularly well to the substrates bonded via the adhesive layer C or C and / or C′. Since the adhesive layer C or C and / or C′ preferably contains no electrolytes, such as ionic liquids, the components do not need to be adapted accordingly.

[0243] Preferably, the adhesive of the adhesive layer D is non-pressure-sensitive adhesive and is therefore preferably not a pressure-sensitive adhesive and the adhesive layer D is therefore preferably not a pressure-sensitive adhesive layer D.

[0244] According to a preferred embodiment, the adhesive of the adhesive layer C or C and / or C′ is also not a pressure-sensitive adhesive.

[0245] According to a further preferred embodiment of the present invention, the adhesive of the adhesive layer C or C and / or C′ is a pressure-sensitive adhesive and the adhesive layer C or C and / or C′ is therefore a pressure-sensitive adhesive layer.

[0246] As is generally customary, pressure-sensitive adhesives are understood according to the invention in this specification to mean substances that are permanently tacky and adhesive (especially at room temperature). Pressure-sensitive adhesives are characterized in that they can be applied to a substrate by pressure and remain adhered there, without having to define in detail the pressure to be applied and the duration of the action of this pressure. In some cases, depending on the exact nature of the pressure-sensitive adhesive, the temperature and air humidity and the substrate, the action of a short minimum pressure of no more than a gentle contact for a short time is sufficient to achieve the adhesive effect, in other cases, a longer action time of high pressure may also be necessary.

[0247] Pressure-sensitive adhesives have specific characteristic viscoelastic properties, which lead to long-lasting (permanent) adhesiveness and adhesiveness. Their characteristic is that when they are mechanically deformed, there is both a viscous flow process and the formation of elastic restoring forces. The two processes are in a specific relationship to each other in terms of their respective proportions, which depends not only on the precise composition, structure and degree of crosslinking of the pressure-sensitive adhesive substance, but also on the rate and duration of deformation, and on the temperature.

[0248] Proportional (a certain proportion) viscous flow is necessary for the realization of adhesion. The viscous components (components) produced only by the macromolecules with relatively large mobility allow effective wetting of the substrate to be bonded and effectively flow thereon. High viscous flow components cause high pressure-sensitive adhesive (also referred to as viscosity or surface viscosity) and therefore often also cause high adhesion. Due to the lack of flowable components, in general, highly crosslinked systems, crystalline or glass-like cured polymers at least have only very little pressure-sensitive adhesive or do not have pressure-sensitive adhesive.

[0249] Proportional (a certain proportion) elastic resilience forces are necessary for the realization of cohesion. They are generated, for example, by very long-chain and highly coiled macromolecules and by physical or chemical crosslinking and allow the forces acting on the adhesive bond to be transmitted. They lead to the adhesive bond being able to fully withstand the long-term loads acting on it (for example in the form of long-term shear loads) for a relatively long time.

[0250] In order to more precisely describe and quantify the extent of the elastic and viscous components, as well as the relationship between the components, variables that can be measured with the help of dynamic mechanical analysis (DMA) can be used: storage modulus (G') and loss modulus (G") . G' is a measure of the elastic component of the material, G" is a measure of the viscous component of the material. Both parameters depend on the deformation frequency and the temperature.

[0251] The variables can be determined with the aid of a rheometer. Here, for example, the material to be investigated is exposed to a sinusoidally oscillating shear stress in a plate-plate arrangement. In the case of an instrument operating in shear stress control, the deformation is measured as a function of time and the time shift of this deformation is measured relative to the introduction of the shear stress. This time shift is referred to as the phase angle δ.

[0252] The storage modulus G′ is defined as follows:

[0253] G′=(τ / γ)·cos(δ) (τ=shear stress, γ=deformation, δ=phase angle=phase shift between shear stress vector and deformation vector).

[0254] The loss modulus G″ is defined as follows:

[0255] G″=(τ / γ)·sin(δ) (τ=shear stress, γ=deformation, δ=phase angle=phase shift between shear stress vector and deformation vector).

[0256] If at room temperature, defined here as 23°C, at 10 0 Up to 10 1 rad / s (radians / s), G′ is at least partially located in the range of 10 3 Up to 10 7 Pa, and if G" also lies at least partially in this range, the substance is generally regarded as pressure-sensitively adhesive and is defined as pressure-sensitively adhesive in the sense of the present invention. "Partially" means that at least a part (at least a section) of the G' curve lies within the range from 10 0 rad / sec (including endpoints) to 10 1 rad / s (including the end points) and the deformation frequency range (abscissa) from 10 3 (Inclusive of endpoints) Pa to 10 7 The range of G' values ​​(ordinate) for Pa (including the endpoints) is within the window spanned by this. For G", this applies correspondingly.

[0257] Preferably, the pressure-sensitive adhesive has a thermal conductivity of 10 0 Up to 10 1 rad / s deformation frequency range and the storage modulus G′ in the range of 10 3 Up to 10 7 Pa range of loss modulus G".

[0258] In order to achieve viscoelastic properties, the monomers on which the polymer on which the pressure-sensitive adhesive is based and the optionally present other components of the pressure-sensitive adhesive are particularly selected so that the pressure-sensitive adhesive has a glass transition temperature (according to DIN 53765) below the use temperature, i.e., typically below room temperature (23° C.). The temperature range in which the polymer substance has pressure-sensitive adhesive properties can be expanded and / or shifted by suitable cohesion-enhancing measures such as crosslinking reactions (forming bridges between macromolecules). Thus, the application range of the pressure-sensitive adhesive can be optimized via the adjustment between the flowability and cohesion of the substance.

[0259] In particular, the pressure-sensitive adhesive has a glass transition temperature, determined in accordance with DIN 53765, of ≤23° C.

[0260] A further subject matter of the invention is a method for producing the adhesive tape according to the invention.

[0261] The adhesive of the adhesive layer D and, depending on the embodiment, the further adhesives are produced by known methods and applied in the form of layers, in particular by coating.

[0262] Furthermore, one or more drying steps may optionally be carried out.

[0263] A plurality of layers are laminated together in a manner known to the person skilled in the art, wherein the layers are stacked in such a way that in particular a layer composite DC or DTC is obtained, with T arranged between D and C, or a C'-T'-DTC as a double-sided tape.

[0264] As mentioned above, the carrier layer T or T' can be provided in different ways.

[0265] It is therefore conceivable to place a) a metal foil, in particular an aluminum foil, and / or b) a conductive mesh and / or d) at least one metal grid and / or e) a metal-evaporated PET foil between the respective adhesive layers.

[0266] In addition, c) the metal particles may be directly evaporated onto the surface of the adhesive layer D, C or C'.

[0267] A further subject matter of the present invention is the production of bonded composites using the adhesive tapes according to the invention.

[0268] In order to activate the reactive heat-activatable adhesive of the adhesive tape according to the invention, it is placed between the substrates to be bonded and preferably heated using compressive pressure, wherein all the above embodiments apply to the activation of the bonding mechanism. In addition, preferably, as described above, pre-lamination is also performed.

[0269] The adhesive tape according to the invention represents in particular a double-sided adhesive tape in which, depending on the embodiment, both sides of the adhesive layer D (transfer tape) or one side of the first adhesive layer D and one side of the second adhesive layer C (two-layer composite DC or three-layer composite DTC) or one side each of the adhesive layers C and C' (five-layer composite CTD-T'-C') can be used in each case for bonding the substrates.

[0270] Advantageously, the exposed outer surface of the adhesive layer of the adhesive tape according to the invention can be provided with an anti-adhesive material, such as a release paper or a release film (also referred to as a liner). In the liner, it can also be a material that is anti-adhesive coated (with an anti-adhesive coating) on ​​at least one side, preferably on both sides, for example a siliconized material on both sides. The liner, or more generally, the temporary carrier, is not part of the adhesive tape, but is merely an aid for its manufacture, storage and / or further processing by stamping. In addition, unlike a permanent carrier, the liner is not firmly bonded to the adhesive layer, but acts as a temporary carrier, i.e. a carrier that can be removed from the adhesive layer. "Permanent carrier" is also referred to synonymously in this application as "carrier".

[0271] The thickness of the individual adhesive layers (in the z direction) is preferably from 10 to 300 μm, particularly preferably from 15 to 150 μm, very particularly preferably from 20 to 100 μm, very particularly preferably from 25 to 70 μm.

[0272] In the embodiments of the double-layer composite DC, the three-layer composite DTC and the five-layer composite CTD-T'-C', the adhesive layers D and C or D and C and D and C' have different layer thicknesses according to a preferred embodiment, wherein the thickness of the adhesive layer D is, for example, smaller than the thickness of the adhesive layer C or C and C'.

[0273] According to a further preferred embodiment, the layers D and C or D, C and C′ have the same layer thickness.

[0274] If the layer thickness of layer D is too high, this can be uneconomically cost-intensive due to the electrolyte contained.

[0275] In the following, preferred embodiments of the present invention are explained and described in more detail with reference to the accompanying drawings. The accompanying drawings show:

[0276] Figure 1 a simplified schematic cross-sectional view through a double-sided adhesive tape according to the invention in a preferred embodiment; and

[0277] Figure 2 a simplified schematic cross-sectional view through a double-sided adhesive tape according to the invention in a preferred embodiment; and

[0278] Figure 3a simplified schematic cross-sectional view through a double-sided adhesive tape according to the invention in a preferred embodiment; and

[0279] Figure 4 a simplified schematic cross-sectional view through a bonded composite according to the invention in a preferred embodiment; and

[0280] Figure 5 a simplified schematic cross-sectional view of a bonded composite according to the invention with a voltage applied thereto throughout a preferred embodiment; and

[0281] Figure 6 A simplified schematic cross-sectional view through a bonded composite according to the invention after application of a voltage and thus adhesive cleavage; and

[0282] Figure 7 Simplified schematic cross-sectional views of a bonded composite according to the invention through a preferred embodiment; and

[0283] Figure 8 Simplified schematic cross-sectional view of a bonded composite according to the invention through a preferred embodiment.

[0284] Fig. 9 A simplified schematic cross-sectional view of a double-sided adhesive tape according to the invention through a preferred embodiment; and

[0285] Fig.10 a simplified schematic cross-sectional view of a bonded composite according to the invention with a voltage applied thereto throughout a preferred embodiment; and

[0286] Fig.11 Simplified schematic cross-section through a bonded composite according to the invention after application of a voltage and thus adhesive cleavage.

[0287] like Figure 1 As shown in FIG, the adhesive layer D1 is bonded via one of its faces to the carrier layer T2. On the face of the carrier layer T opposite to the layer D, a second adhesive layer C3 is arranged.

[0288] As in Figure 1 As can likewise be seen in FIG. 1 , the layer composite represents a double-sided adhesive tape, wherein the side of the adhesive layer D and the side of the second adhesive layer C are available in each case for bonding.

[0289] exist Figure 2 A preferred embodiment of the present invention is shown in . In this case, the conductive carrier layer T2 protrudes laterally beyond the adhesive layer D1 and the second adhesive layer C3 in at least one extension direction of the layer plane, so that the conductive carrier layer T2 has a protrusion with at least one free surface 2a.

[0290] Figure 3 A further preferred embodiment of the present invention is shown in FIG. Here, the conductive carrier layer T 2 protrudes laterally beyond the adhesive layer D 1 in at least one extension direction of the layer plane, so that the conductive carrier layer T 2 has a protrusion with a free surface 2 a. Figure 3 The middle adhesive layer C3 is designed such that it also has a protrusion relative to the layer D1. In particular, the carrier layer T2 is a PET film coated with aluminum on one side, wherein the aluminum-coated side is bonded to the layer D1.

[0291] Figure 4 A schematic diagram of a bonded composite according to the invention in a preferred embodiment is shown in FIG. Figure 4 As can be seen in FIG. 1 , the adhesive tape is arranged on the surface of the first substrate A 4 via the adhesive layer D1 , wherein the first substrate is conductive.

[0292] Furthermore, the adhesive tape is arranged on the face of the second substrate B5 via a second adhesive layer C3.

[0293] exist Figure 4 , it is also shown by way of example that the electrically conductive carrier layer T2 protrudes laterally beyond the first adhesive layer D1 in at least one extension direction of the layer plane, so that the electrically conductive carrier layer T has a protrusion having a free surface 2a.

[0294] Now a voltage can be applied to the free surface 2a, as in Figure 5 As shown in the schematic diagram.

[0295] By applying a voltage, migration of the electrolyte, in particular separation of anions and cations of the ionic liquid, occurs in the adhesive layer D1.

[0296] As a result, the adhesion of the adhesive layer D1 to the substrate A4 is greatly reduced, and the layers are separated from each other, as shown in FIG. Figure 6 As shown in the schematic diagram.

[0297] exist Figure 7 A further schematic diagram of a bonded composite according to the invention in a preferred embodiment is shown in FIG. Figure 7 As can be seen in FIG. 1 , the adhesive tape is arranged on the face of the first substrate A4 via the adhesive layer C 3 .

[0298] Furthermore, the adhesive tape is arranged on the face of the second substrate B5 via a third adhesive layer C'7.

[0299] Between the layers C3 and C′7 there is an electrically separable adhesive layer D1 and two electrically conductive carrier layers T2 and T′6 , wherein the layer D1 is arranged between the carrier layers.

[0300] exist Figure 7It is also shown by way of example that the conductive carrier layer T2 and the conductive carrier T'6 respectively protrude laterally from the first adhesive layer D1 in at least one extension direction of the layer plane, so that the conductive carrier layer T has a protrusion with a free surface 2a and the conductive carrier T'6 has a protrusion with a free surface 6a.

[0301] exist Figure 8 A further schematic diagram of a bonded composite according to the invention in a preferred embodiment is shown in FIG. Figure 7 However, unlike Figure 7 Differently, the projections of the electrically conductive carrier layer T2 and of the electrically conductive carrier layer T′6 point in different directions, so that the resulting free surfaces 2 a or 6 a of these layers are spatially separated.

[0302] Now a voltage can be applied to these free surfaces 2a and 6a, similar to Figure 5 . According to Figure 5 Unlike the embodiment of the present invention, a voltage can be applied to both surfaces 2a and 6a, so that neither substrate A nor B need to be electrically conductive.

[0303] By applying a voltage, the migration of electrolytes, in particular the separation of anions and cations of the ionic liquid, occurs in the adhesive layer D1. As a result, the adhesion of the adhesive layer D1 to the carrier layer T2 and / or T'6 is greatly reduced, and these layers are separated from each other. In particular, separation occurs at the layer where the negative electrode is applied.

[0304] In accordance with Figure 8 The application of the voltage is simplified in the case of spatially separated surfaces 2 a and 6 a.

[0305] exist Fig. 9 Schematically shown in FIG. 1 is a two-layer composite consisting of an electrically separable adhesive layer D 1 and a second adhesive layer C 3 which contains an electrolyte.

[0306] Preferably, the second adhesive layer, particularly in this embodiment, is electrically conductive.

[0307] Thus, voltage can be applied to them, e.g. Fig.10 As shown in Fig.10 As shown in , the conductive layer C3 here protrudes laterally from the substrate 5, thereby providing a free surface 3a to which a voltage can be applied. Therefore, the voltage is applied here at a position of the layer C close to the substrate 5, rather than laterally.

[0308] By applying a voltage, the adhesion between the adhesive layer D1 and the substrate A4 is also reduced, so that the substrate and the adhesive layer are separated from each other, as shown in FIG. Fig.11 as shown in .

[0309] Figures 1 to 11The figure in is a schematic diagram of the invention. In particular, the layer thicknesses of the individual layers D, T and C may differ from one another. In addition, the substrates A and B are also only schematically shown as further layers. Of course, these may have any other spatial geometry.

[0310] Hereinafter, some examples are described to further illustrate the present invention.

[0311] Test Method

[0312] Unless otherwise specified, all measurements are carried out at 23°C and 50% relative air humidity. The mechanical and adhesive technical data are determined as follows:

[0313] Molecular weight n 、M w

[0314] The number average molecular weight M in this specification n Or weight average molecular weight M w The data relate to determinations by gel permeation chromatography (GPC). The determinations were carried out on 100 μl of the sample subjected to clarification filtration (sample concentration 4 g / l). The eluent used was tetrahydrofuran with 0.1% by volume of trifluoroacetic acid. The measurements were carried out at 25° C. The preparatory column used was a PSS-SDV type column, 5 μm, 8.0mm*50mm (here and below, described in the following order: type, particle size, porosity, inner diameter*length; Use type PSS-SDV, 5μm, as well as and The separation was performed using a combination of 10 columns (each 8.0 mm × 300 mm) (columns from Polymer Standards Service; detection by means of a differential refractometer Shodex RI71). The flow rate was 1.0 ml / min. For polar molecules, calibration was performed against PMMA standards (polymethyl methacrylate calibration), otherwise calibration was performed against PS standards (polystyrene calibration).

[0315] thickness

[0316] The thickness of the adhesive layer can be determined by measuring the thickness of a portion (segment) of such adhesive layer applied to the liner, defined according to its length and its width, minus the thickness of a portion (segment) of the liner used with the same dimensions (known or individually determinable). Commercial thickness gauges (probe instruments) with an accuracy of less than 1 μm deviation can be used to determine the thickness of the adhesive layer. If fluctuations in the thickness are determined, the average value of the measured values ​​at at least three representative locations is reported, i.e. in particular not measuring at folds, creases, tips, etc.

[0317] Like the thickness of the adhesive layer, the thickness of the adhesive tape (adhesive strip) or carrier can also be determined analogously using a commercial thickness gauge (probe instrument) with an accuracy of less than 1 μm deviation. If fluctuations in the thickness are determined, the average of the measured values ​​at at least three representative locations is reported, i.e. in particular not measuring at folds, creases, tips, etc.

[0318] Adhesion Strength-Shear Strength

[0319] As a parameter for the quality of the bond achieved, the bond strength of the bonded composite of the adhesive tape to be tested was determined. For this purpose, the shear strength was quantitatively determined in accordance with DIN-EN 1465 at 23° C. and 50% relative humidity in a dynamic tensile shear test at a test speed of 10 mm / min (results in N / mm 2 = MPa). As test specimens, steel ones are used which have been cleaned with acetone before bonding. The provision of test specimens and the layer thickness of the adhesive tape should comply with the following regulations.

[0320] The average of three measurements is given.

[0321] The following example according to the invention of an adhesive tape comprising at least one adhesive layer D was prepared, bonded between substrates and then electrically separated again by applying a voltage. In this case, the adhesive of the layer D was a heat-activatable, non-pressure-sensitive adhesive before activation in each case.

[0322] Table 1: Chemicals used:

[0323]

[0324] Transfer tapes according to Examples 1 to 3

[0325] Embodiment 1 according to the present invention

[0326] The adhesive layer D is provided as follows:

[0327] Based on the total amount of the later adhesive without solvent, 87.0 wt.% of 530 (polyurethane) was dissolved in MEK.

[0328] Subsequently, 10.0 wt% of 999 and mix thoroughly with the dissolved polyurethane.

[0329] Then, 3.0 wt% of the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-TFSI) was added and also mixed thoroughly.

[0330] The heat-activatable adhesive was then spread from the solution onto a translucent release paper and dried for 20 minutes at 50° C. After drying, the layer thickness was 30 μm.

[0331] Embodiment 2 according to the present invention

[0332] The adhesive layer D is provided as follows:

[0333] 100 parts by weight of aqueous PU dispersion Dispercoll U53 (Covestro) were provided, 10 parts by weight of Dispercoll BL XP 2514 (Covestro) and 1.5 parts by weight of Borchigel 0625 were added and mixed thoroughly with the PU dispersion.

[0334] Subsequently, 3.0 parts by weight of ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide salt (EMIM-TFSI) was added and also mixed thoroughly.

[0335] The heat-activatable adhesive was then spread from the thickened aqueous solution onto a translucent release paper and dried for 20 minutes at 50° C. After drying, the layer thickness was 30 μm.

[0336] Embodiment 3 according to the present invention

[0337] The adhesive layer D is provided as follows:

[0338] Based on the total amount of the later adhesive without solvent, 89.0 wt% of 530 (polyurethane) was dissolved in MEK.

[0339] Subsequently, 5.0 wt % of dicumyl peroxide and 3 wt % of 3-methacryloxypropyltriethoxysilane were added and mixed thoroughly with the dissolved polyurethane.

[0340] Then, 3.0 wt% of the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-TFSI) was added and also mixed thoroughly.

[0341] The heat-activatable adhesive was then spread from the thickened aqueous solution onto a translucent release paper and dried for 20 minutes at 50° C. After drying, the layer thickness was 30 μm.

[0342] Furthermore, in Example 4, an example according to the invention of a two-layer composite DC was produced. Adhesives D and C were in each case heat-activatable, non-pressure-sensitive adhesives before activation.

[0343] Embodiment 4 according to the present invention

[0344] The adhesive layer D is provided as follows:

[0345] Based on the total amount of the later adhesive without solvent, 87.0 wt.% of 530 (polyurethane) was dissolved in MEK.

[0346] Subsequently, 10.0 wt% of 999 and mix thoroughly with the dissolved polyurethane.

[0347] Then, 3.0 wt% of the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-TFSI) was added and also mixed thoroughly.

[0348] The heat-activatable adhesive was then spread from the solution onto a translucent release paper and dried for 20 minutes at 50° C. After drying, the layer thickness was 30 μm.

[0349] The adhesive layer C is provided as a conductive adhesive layer as follows:

[0350] 36.0% by weight of Desmomelt 530 (polyurethane), based on the total amount of the later adhesive without solvent, were dissolved in MEK.

[0351] Subsequently, 4.0 wt% of 999 and mix thoroughly with the dissolved polyurethane.

[0352] Then, 60% by weight of nickel particles (average particle size 4 μm: T 123, Vale Canada Ltd.) were added and likewise mixed thoroughly.

[0353] The heat-activatable adhesive was then spread from the solution onto a separate translucent release paper and dried for 20 minutes at 50° C. After drying, the layer thickness was 30 μm.

[0354] The two layers D and C were placed one on top of the other in a bubble-free manner using a rubber roller and passed through a hot laminator at 70° C. at a speed of 1 m / min.

[0355] To test the bonding strength, the corresponding adhesive tapes (transfer tapes according to Examples 1 to 3 and the adhesive tape with a two-layer structure according to Example 4) were bonded between two steel plates as follows:

[0356] Cut three pieces of approximately 15 x 25 mm from the tape to be tested (covered with release paper on one side). 2 Blocks of size.

[0357] The test specimen made of steel (substrate) was placed on a hot plate preheated to 70° C. After about five seconds of tempering, the open side of the tape sample not covered with release paper was applied to the surface of the sample with the aid of tweezers and pressed down smoothly with a rubber roller.

[0358] Embodiments 1 to 3:

[0359] After cooling, the protruding tape edges are cut off and the release paper is removed. The second test specimen is placed on a hot plate preheated to 70° C. for 5 seconds and tempered. The coated strip (tape on the first steel substrate) is applied with an overlap of exactly 10 mm and pressed thereon. Subsequently, the composite thus prelaminated is allowed to cool.

[0360] Embodiment 4:

[0361] After cooling, the protruding tape edge is cut off (but a 2 cm long tape strip is left on one side) and the release paper is removed. The second test specimen is placed on a hot plate preheated to 70° C. for 5 seconds and tempered. The coated strip (tape on the first steel substrate) is applied with an overlap of exactly 10 mm and pressed thereon. Subsequently, the composite thus prelaminated is allowed to cool.

[0362] Subsequently, activation takes place in each case by supplying heat and pressure in a hot press.

[0363] In Example 1 according to the invention, heating was carried out for 5 minutes to a temperature of 100° C. at a pressure of 10 bar.

[0364] In Example 2 according to the invention, heating was carried out at a pressure of 5 bar for 2 minutes to a temperature of 90°C.

[0365] In Example 3 according to the invention, heating was carried out at a pressure of 5 bar for 5 minutes to a temperature of 150° C.

[0366] In Example 4 according to the invention, heating was carried out for 5 minutes to a temperature of 100° C. at a pressure of 10 bar.

[0367] The samples obtained were stored at room temperature and 50% relative humidity (standard climate) for 24 hours.

[0368] The adhesive strength was determined according to the method described above. The results are summarized in Table 2.

[0369] Then, the samples of Examples 1 to 4 described above were prepared again and tested for electrical re-separability.

[0370] After bonding and activation, a voltage was applied in each case to the two steel sheets representing the conductive substrates A and B in Examples 1 to 3 and to the steel sheet combined with layer D and to the conductive layer C in Example 4, and specifically to a 2 cm wide side strip of the adhesive tape.

[0371] The voltage was 1 to 48 V and applied for 5 minutes in Examples 1 to 3, and was 12 V and applied for 3 minutes in Example 4.

[0372] The adhesive strength was determined according to the method described above. The results are also summarized in Table 2.

[0373] Table 2

[0374]

[0375] As shown in the tests for adhesive strength and re-separability in Examples 1, 2, 3 and 4 according to the present invention, before the application of voltage, the adhesive layer D has a large adhesive strength to a substrate such as steel, and is reduced to such a low value only by the application of voltage that the substrates can be separated from each other quickly and effortlessly, and there is no residue associated with the adhesive of layer D.

[0376] As can be seen from the values ​​in Table 2, the adhesive strength can be significantly reduced here by applying a voltage.

[0377] Thus, surprisingly, electrically separable reactive heat-activatable adhesive tapes or bonded composites comprising heat-activated adhesive tapes have been successfully provided.

[0378] Reference numerals list

[0379] 1 Adhesive layer D

[0380] 2 Conductive carrier layer T

[0381] 2a Free surface of the conductive carrier layer T

[0382] 3 Second adhesive layer C

[0383] 3a Free surface of adhesive layer C

[0384] 4First substrate A

[0385] 5 Second substrate B

[0386] 6 Second conductive carrier layer T'

[0387] 6a Free surface of the conductive carrier layer T'

[0388] 7 Third adhesive layer C'

Claims

1. Adhesive tape comprising at least one adhesive layer D, wherein the adhesive of the adhesive layer D is a heat-activatable adhesive and contains at least one electrolyte.

2. The adhesive tape according to claim 1, characterized in that The electrolyte of the adhesive layer D is selected from ionic liquids and metal salts, among which ionic liquids are particularly preferred.

3. The adhesive tape according to claim 2, characterized in that The anion of the ionic liquid is selected from Br - 、AlCl4 - 、Al2Cl7 - 、NO3 - 、BF4 - PF6 - 、CH3COO - CF3COO - CF3CO3 - CF3SO3 - 、(CF3SO2)2N - 、(CF3SO2)3C - 、AsF6 - 、SbF6 - CF3(CF2)3SO3 - 、(CF3CF2SO2)2N - CF3CF2CF2COO - 、(FSO2)2N - , and in this case particularly preferably selected from (CF3SO2)2N - and (FSO2)2N - , and / or the cation of the ionic liquid is selected from imidazolium-based cations, pyridinium-based cations, pyrrolidine-based cations and ammonium-based cations, and in this case particularly preferably from imidazolium-based cations, wherein the cation is particularly preferably selected from 1-ethyl-3-methylimidazolium and 1-butyl-3-methylimidazolium, wherein the cation is very particularly preferably 1-ethyl-3-methylimidazolium.

4. Adhesive tape according to one of the preceding claims, characterized in that The electrolyte of the adhesive layer D is selected from the following ionic liquids: 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-TFSI) and 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMIM-FSI).

5. Adhesive tape according to one of the preceding claims, characterized in that The first adhesive layer D contains 1 to 10% by weight, preferably 2 to 8% by weight, of an electrolyte, preferably an ionic liquid, based on the total amount of the adhesive.

6. Adhesive tape according to one of the preceding claims, characterized in that The heat-activatable adhesive of the adhesive layer D is a reactive heat-activatable adhesive or a physically heat-activatable adhesive, wherein it is particularly preferably a reactive heat-activatable adhesive.

7. Adhesive tape according to one of the preceding claims, characterized in that The heat-activatable adhesive of the adhesive layer D comprises a polymer component formed from at least one thermoplastic elastomer, preferably a thermoplastic polyurethane.

8. The adhesive tape according to claim 7, characterized in that The heat-activatable adhesive of adhesive layer D is a reactive heat-activatable adhesive, and the polymer component is formed by at least one polymer containing functional groups capable of reacting with isocyanate, and the reactive heat-activatable adhesive of adhesive layer D also includes a crosslinker component formed by at least one isocyanate-containing compound, wherein the reactive heat-activatable adhesive of adhesive layer D preferably further includes at least one additional component from the group of epoxides and / or epoxy compounds.

9. The adhesive tape according to claim 7, characterized in that The heat-activatable adhesive of the adhesive layer D is a reactive heat-activatable adhesive, and the reactive heat-activatable adhesive of the adhesive layer D further comprises at least one peroxide, wherein the peroxide is preferably dicumyl peroxide.

10. The adhesive tape according to any one of claims 1 to 9, characterized in that The adhesive tape is a transfer tape and consists of an adhesive layer D.

11. The adhesive tape according to any one of claims 1 to 9, characterized in that It further comprises at least one second adhesive layer C, wherein the second adhesive layer is preferably electrically conductive.

12. The adhesive tape according to any one of claims 1 to 9, characterized in that It additionally comprises at least the following layers: A second adhesive layer C; and • At least one electrically conductive carrier layer T arranged between layers D and C.

13. The adhesive tape according to any one of claims 1 to 9, characterized in that It additionally comprises at least the following layers: A second adhesive layer C; and at least one first electrically conductive carrier layer T arranged between layers D and C; and at least one second electrically conductive carrier layer T′ arranged on the face of the adhesive layer D opposite to the first electrically conductive carrier layer T; and • A third adhesive layer C' arranged on the side of the second carrier layer T' opposite the first adhesive layer D.

14. A bonded composite comprising at least the following layers: A first substrate A; and A second substrate B; and The adhesive tape according to any one of claims 1 to 13, which is arranged between a substrate A and a substrate B and bonds the substrates A and B to each other.

15. A method for the electrical separation of a complex according to claim 14, comprising at least the following method steps: i.) applying a voltage at two different sites of the complex, wherein the voltage is preferably 2 to 50V.

16. Use of the adhesive tape according to any one of claims 1 to 13 for bonding components in electronic devices, automobiles, medical devices and dental devices.

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